1. Field of the Invention
The present invention relates to the field of displaying, and in particular to a method for manufacturing an assembly of a flexible display device and an assembly of a flexible display device manufactured with same.
2. The Related Arts
With the vivid and vigorous progress of displaying techniques and information devices, display devices have been evolved from the traditional cathode ray tubes (CRTs) to a flat panel display (FPD) era. A flexible display device, compared with a conventional rigid glass panel display device, possesses properties including being thinner and lighter, being flexible, being resistant to impact, and safety and is generally not constrained by location and space, thereby becoming the new trend of development of the next generation display devices.
A flexible thin-film transistor (TFT) substrate is one of the key components of the flexible display device and selection and development of substrate material is the most important issue for the development of the flexible display device. Heretofore, the available choices for flexible substrate materials include a plastic substrate, a thin glass substrate, and a metal foil, among which the plastic substrate enables the realization of being lighter and thinner, impact resistance, and reduced cost; however, the plastic substrate suffers shortcomings including being incapable of high temperature processes and having a relatively high thermal expansion coefficient.
Referring to FIG. 1, a schematic view is given to show the structure of a conventional flexible TFT substrate, which comprises: a glass substrate 100, a flexible base 300 formed on the glass substrate 100, a protective layer 500 formed on the flexible base 300, a low-temperature polysilicon layer 700, and a TFT array (not shown) formed on the low-temperature polysilicon layer 700, wherein the protective layer 500 comprises a silicon nitride layer 502 formed on the flexible base 300 and a silicon oxide layer 504 formed on the silicon nitride layer 502. The low-temperature polysilicon layer 700 is generally formed by annealing an amorphous silicon layer and further, the formation of the low-temperature polysilicon layer 700 also requires activation by laser. Laser activation generation a great amount of heat. The heat, when transmitted to the flexible base 300, may cause deformation of the flexible base 300, severely affecting the quality of the flexible TFT substrate.
As shown in FIG. 2, to overcome such a problem, another flexible TFT substrate that is currently available increases the thickness of the silicon oxide layer 504′ of the protective layer 500′ (from approximately 500 nm to 1-2 μm) in order to block the transmission of heat to the flexible base 300. However, although such a measure reduces, to some extents, the possibility of deformation of the flexible base 300, an excessively large thickness of the silicon oxide layer 504′ would lead to an excessive stress, thereby affecting the curving performance of the flexible TFT substrate and also potentially causing other issues such as poor crystallization of the low-temperature polysilicon layer 700.